From 6f70c5585f600d178c1bef4bd63bbe1d527ac44a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Manuel=20Tom=C3=A1s?= <jtomas1815@gmail.com>
Date: Sat, 12 Nov 2022 03:16:55 -0300
Subject: Better error reporting for numbers

If sign has been parsed, there must be a natural after it.
---
 json.lisp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/json.lisp b/json.lisp
index 6fe95b8..23c9198 100644
--- a/json.lisp
+++ b/json.lisp
@@ -12,7 +12,10 @@
 (defparameter number-literal
   (let ((signed-digits
           (comp ((sign (zero-or-one (some-char #\- #\+)))
-                 (natural (one-or-more (unit #'digit-char-p))))
+                 (natural (if sign
+                            (either (one-or-more (unit #'digit-char-p))
+                                    (fail "Malformed number."))
+                            (one-or-more (unit #'digit-char-p)))))
             (cons sign natural))))
     (comp ((base signed-digits)
            (dot (zero-or-one (the-char #\.)))
-- 
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